Recently, a new class of thermoelastic sulfonated polymers has been described in a number of U.S. patents. These sulfonated polymers are derived from polymeric materials having olefinic unsaturation, especially elastomeric polymers such as Butyl and EPDM rubbers. U.S. Pat. No. 3,642,728, herein incorporated by reference, clearly teaches a method of selective sulfonation of olefinic unsaturation sites of an elastomeric polymer to form an acid form of a sulfonated elastomeric polymer. The olefinic sites of the elastomeric polymer are sulfonated by means of a complex of a sulfur trioxide donor and a Lewis base. The sulfonated elastomer can be readily neutralized with a basic material to form an ionically cross-linked elastomer having substantially improved physical properties over an unsulfonated elastomer at room temperature. However, these ionically cross-linked elastomers, may be processed like conventional thermoplastics at elevated temperatures under a shear force in the presence of selected preferential plasticizers which dissipate the ionic associations at the elevated temperatures thereby creating a reprocessable elastomer.
The basic materials used as neutralizing agents are selected from organic amine or basic materials selected from Groups I, II, III, IV, V, VI-B, VIIB and VIII and mixtures thereof of the Periodic Table of Elements. Although these sulfonated elastomeric polymers prepared by the process of this patent are readily usable in a certain number of limited applications, they are not as readily adaptable for the manufacture of an extrudable and injection moldable elastomeric article as are the improved compositions of the present invention, wherein both improved physical and rheological properties are realized.
U.S. Pat. No. 3,836,511, herein incorporated by reference, teaches an improved process for the sulfonation of the olefinic sites of the elastomeric polymer, wherein the improved sulfonating agent is selected from acetyl sulfate, propionyl sulfate and butyryl sulfate. The neutralizing agents employed to neutralize the acid form of the sulfonated elastomeric polymers are organic amines. The resultant ionically cross-linked sulfonated elastomers prepared by this process do not exhibit both the improved physical and rheological properties of the compositions of the present invention.
U.S. Pat. No. 3,870,841, herein incorporated by reference, teaches a method of plasticization of the polymeric backbone of a neutralized sulfonated plastic polymer by means of a polymer chain plasticizer which is a liquid compound having a boiling point of at least about 120.degree. F. The polymer chain plasticizer is selected from a dialkyl phthalate, a process oil or an organic acid ester. Additionally, a domain plasticizer can be incorporated into the composition, wherein the domain plasticizer reversibly disrupts the association of the sulfonated groups at a temperature of forming. The compositions formed by this process are not as suitable for the manufacture of high performance elastomeric articles formed by extrusion or injection molding process as are the compositions of the present invention.
U.S. Pat. No. 3,847,854, herein incorporated by reference, teaches a method of improving the processability of neutralized sulfonated elastomeric polymers by the addition of a preferential plasticizer which has at least one functional constituent which exhibits a bond moment whose absolute value is at least 0.6 Debyes, and must be a liquid at the desired processing temperature of the neutralized sulfonated elastomeric polymer. Again, the compositions of the present invention are more adaptable for use in the manufacture of high performance elastomeric articles.
Products resulting from the aforementioned methods for obtaining neutralized sulfonated elastomeric compositions possess either unsuitable rheological or physical properties for the applications envisioned in the present invention.
For example, the resultant sulfonated elastomeric compounds designed for extruded applications, namely, for the manufacture of garden hose, display excellent physical properties in many respects such as resilience, low and high temperature flexibility, flex fatigue, etc. However, those compounds displaying these highly desired characteristics also can display high melt viscosity and melt elasticity which makes smooth extrusion at desirably high production rates very difficult, if not impossible. Consequently, such systems are difficult to process in the equipment which is required to make the shape for which these compounds were originally designed.
It would be extremely desirable to develop such compounds which display the desirable balance of physical properties and processability needed for such extrusion applications. The same comments also apply to injection molding compounds. In addition it is highly desired and indeed essential that this balance be achieved at relatively low compound costs in order that these systems can compete economically for such cost conscious applications.
U.S. Pat. No. 3,974,240 and 3,974,241 issued on Aug. 10, 1976 describe the blending of a crystalline polyolefinic material with a neutralized sulfonated elastomeric polymer in an attempt to improve both the rheological and physical properties of the elastomeric polymer. The selection of the use of the crystalline polyolefinic material to improve both the stiffness as well as improving the melt viscosity of the composition was based in part upon the limitation of the use of fillers such as carbon black, clays, calcium carbonate or silicates as a single additive to the elastomeric polymer. Although fillers in combination with an elastomeric polymer increase the hardness of the composition, these fillers deteriorate the melt viscosity of the resultant composition.
The unique and novel compositions of the present invention overcome the deficiencies of the aforementioned U.S. patents and applications from both a rheological and physical properties aspect. The blend compositions of the present invention contribute to solution of having a material which has both desirable rheological and physical properties.
For example, the incorporation of a crystalline polyolefin, such as polyethylene, at even a modest level of 10 wt. % can markedly increase the hardness of an elastomeric composition which can be undesirable for many applications. Similarly, the use of a polar plasticizer to preferentially plasticize the ionic domains provides a blend composition with markedly improved flow behavior but at a substantial sacrifice in physical properties, especially at elevated temperatures.
The present invention teaches a blend composition formed from a sulfonated elastomeric polymer and a non-polar wax, wherein the wax improves the flow properties of the composition without substantially adversely affecting the physical properties.